G.703/G.704 ITU-T electrical and mechanical specifications for connections between telephone company equipment and DTE using BNC connectors and operating at E1 data rates. G.804 ITU-T framing standard that defines the mapping of ATM cells into the physical medium. gateway In the IP community, an older term referring to a routing device. Today, the term router is used to describe nodes that perform this function, and gateway refers to a special-purpose device that performs an application layer conversion of information from one protocol stack to another. Compare with router. Gateway Discovery Protocol See GDP. gateway host In SNA, a host node that contains a gateway SSCP. gateway NCP NCP that connects two or more SNA networks and performs address translation to allow cross-network session traffic. Gateway-to-Gateway Protocol See GGP. GB Gigabyte. GBps Gigabytes per second. Gb Gigabit. Gbps Gigabits per second. GDP Gateway Discovery Protocol. Cisco protocol that allows hosts to dynamically detect the arrival of new routers as well as determine when a router goes down. Based on UDP. See also UDP. generic routing encapsulation See GRE. Get Nearest Server See GNS. GGP Gateway-to-Gateway Protocol. MILNET protocol specifying how core routers (gateways) should exchange reachability and routing information. GGP uses a distributed shortest-path algorithm. GHz Gigahertz. GID Global information distribution. Process that runs on the NP of every LightStream 2020 ATM switch in a network. GID maintains a database and keeps nodes in the network apprised of changes in topology such as ports, cards, and nodes being added or removed, and trunks going up or down. This information is supplied by the ND process. Sometimes called global information distribution daemon, or GIDD. See also ND. GIDD Global information distribution daemon. See GID. gigabit Abbreviated Gb. gigabits per second Abbreviated Gbps. gigabyte Abbreviated GB. gigabytes per second Abbreviated GBps. gigahertz Abbreviated GHz. global configuration database See configuration database. global information distribution See GID. global information distribution daemon See GID. GNS Get Nearest Server. Request packet sent by a client on an IPX network to locate the nearest active server of a particular type. An IPX network client issues a GNS request to solicit either a direct response from a connected server or a response from a router that tells it where on the internetwork the service can be located. GNS is part of the IPX SAP. See also IPX and SAP (Service Advertisement Protocol). GOSIP Government OSI Profile. U.S. government procurement specification for OSI protocols. Through GOSIP, the government has mandated that all federal agencies standardize on OSI and implement OSI-based systems as they become commercially available. Government OSI Profile See GOSIP. grade of service Measure of telephone service quality based on the probability that a call will encounter a busy signal during the busiest hours of the day. graphical user interface See GUI. GRE Generic routing encapsulation. Tunneling protocol developed by Cisco that can encapsulate a wide variety of protocol packet types inside IP tunnels, creating a virtual point-to-point link to Cisco routers at remote points over an IP internetwork. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling using GRE allows network expansion across a single-protocol backbone environment. ground Electrically neutral contact point. ground loop Arrangement that exists when a multi-path connection exists between computers. Usually this occurs when computers are connected to each other through a ground wire and when computers are attached to the same network using twisted pair cable. ground station Collection of communications equipment designed to receive signals from (and usually transmit signals to) satellites. Also called a downlink station. group address See multicast address. group delay See distortion delay. guard band Unused frequency band between two communications channels that provides separation of the channels to prevent mutual interference. GUI Graphical user interface. User environment that uses pictorial as well as textual representations of the input and output of applications and the hierarchical or other data structure in which information is stored. Conventions such as buttons, icons, and windows are typical, and many actions are performed using a pointing device (such as a mouse). Microsoft Windows and the Apple Macintosh are prominent examples of platforms utilizing a GUI. gutter Type of wall-mounted channel with removable cover used to support horizontal cabling. Gutter is big enough to hold several cables.